WASHINGTON, D.C. — The first legal briefs in the U.S. Supreme Court’s case challenging former President Obama’s Clean Water Rule are expected to be filed this week after the high court rebuked efforts by President Trump last week to halt the controversial case.

The justices’ decision came April 3, with no explanation. Under review is the question: Does the Clean Water Act grant federal courts of appeals jurisdiction to review the U.S. EPA’s rule that defines the scope of “waters of the United States” (WOTUS)?

Trump signed an executive order Feb. 28 seeking to roll back the controversial water rule opposed by a number of states, farmers, ranchers and the National Assoc. of Manufacturers, who filed objections against the EPA to block the rule.

WOTUS asserts the federal government’s authority over small waterways such as streams and wetlands in order to protect them from pollution. The rule remains on hold as the Sixth Circuit Court of Appeals in Cincinnati considers challenges from the manufacturers’ group and others, after the appeals court voted 2-1 in February 2016 to decide the case.

The Sixth Circuit decision had consolidated a number of cases filed by other federal circuits and district courts.

The Supreme Court’s decision last week could mean that justices see the case as relevant no matter what Trump decides to do with the regulation. That’s the opinion from Jonathan Adler, a law professor at Case Western University, who has been following the case.

“Given that I suspect the court took the case in the first place because of its interests in this issue, it should not be surprising that the court is not going to let go of the case right now,” Adler said, “and given that we don’t know how quickly the Trump administration will act on WOTUS, it’s possible the courts will begin to rule on its merits of the current rule before a replacement is developed.”

When Trump signed the order, he called WOTUS “one of the worst examples of federal regulation – and it has truly run amok. It’s a horrible, horrible rule,” he said.

Joe Devine, a senior attorney in the National Resources Defense Council’s water program, said, “The (Supreme) Court saw through the Trump administration’s maneuver. The administration brazenly attempted to postpone the Clean Water Rule’s implementation indefinitely, while it goes about gutting protections for water bodies that serve as drinking water supplies, natural flood buffers and protection filters and destinations for countless Americans who swim and fish.”

It’s not unusual for the Supreme Court to issue notices of decisions without giving any details.

Another observer of the case, Larry Liebesman, a senior adviser with the Washington, D.C., water resources consulting firm Dawson & Associates, told the trade publication Environment & Energy News the justices might have been persuaded by the opposition to the Trump administration’s motion to hold the case’s briefing schedule in abeyance.

As the case works its way through the court, new EPA Administrator Scott Pruitt, a longtime opponent of the agency, signaled earlier it is fast-tracking its review of the Obama rule, a process he’s not accustomed to that will still take more than a year.

The first legal merit briefs before the Supreme Court are due April 13, according to the court’s current schedule. The court is expected to hear oral arguments during its fall term and could render a decision by the end of the year.

Rolling back the WOTUS rule won’t be easy. First, Pruitt has to go through the formal federal rulemaking process and replace Obama’s regulation with his own version – and then defend it in court as legally superior. Also confronting him is figuring out which bodies of water deserve protection, a complex task that must meet a set of regulatory standards that could take years.

Pruitt faces legal challenges from environmental groups, too – which could end up back before the Supreme Court.